Powder dosing device

ABSTRACT

The invention relates to a powder measure-dispensing cap ( 1 ) comprising: a body ( 3 ) having a first end face ( 4 ), which is designed to be brought into contact with a powder container ( 10 ), and a second end face ( 5 ) which, together with the first end face ( 4 ), defines at least one feed opening ( 6 ) which flares out towards the first end face ( 4 ), said feed opening ( 6 ) supplying at least one endless screw ( 7 ); and at least one opening ( 12 ). The inventive device is characterised in that the opening ( 12 ) is disposed in the second end face ( 5 ) in contact with the endless screw ( 7 ).

[0001] The present invention relates to a powder dosing device.

[0002] More particularly, the present invention relates to a dosingdevice comprising a powder container and a dosing cap allowing smallmasses of powders to be dispensed with great precision.

[0003] In the chemical and pharmaceutical industry, it is oftennecessary to perform precise weighing operations on reagents or productsin powder form, in particular from collections of chemical compounds.When conducting tests on a large number of powdered products, thesuccessive weighing operations become particularly tedious. They maypose a risk of contamination to the operating personnel or may causedegradation of the product.

[0004] It has therefore been sought to automate these weighingoperations in order to permit the dispensing of defined masses of alarge variety of powders, with the desired precision. Another objectivehas been to safeguard the operating personnel from possiblecontamination while at the same time protecting the product frompossible degradation.

[0005] Patent application FR 2 672 035 describes a device which allowsdefined masses of powders to be dispensed. This device is made up of aflask of powder and a dosing cap. The dosing cap comprises a cylindricalconical body having a first end face communicating with the flask, and asecond end face which defines, together with the first end face, aconical feed hopper which widens toward the first end face.

[0006] The feed hopper supplies an endless screw. The body of the capcomprises an opening positioned on the side of the body of the cap, inthe axis of and at the end of the endless screw. When the flask isturned upside down, the powder fills the feed hopper. By rotating theendless screw, it is possible to dispense controlled quantities ofpowder through the opening.

[0007] The device is entirely adequate for dispensing masses of productsranging from about 5 mg to about 8 mg and above, with a precision of theorder of 1 mg.

[0008] Another device of the same type is described in patentapplication FR 2 775 958. The principle of using a cap provided with anendless screw and with a dispensing opening at the end of the endlessscrew is also already evoked in a document as old as U.S. Pat. No.2,593,803.

[0009] German utility model No. 89 14 389 U in the name of Fink-ChemieGmbH describes a device for dosing of flowing materials, in particularpowders. This device is equipped with an inlet supplying powder to anendless screw. This endless screw conveys the powder toward a dispensingopening formed in the lower surface of the device.

[0010] This device however is not like a dosing cap for precision dosingof small quantities of powders of various types, as is demanded inparticular when working with a collection of chemical compounds. On thecontrary, this device appears to be designed for dosing large masses ofpowders where precision is of less importance. Nor does this utilitymodel mention any dosing precision requirements.

[0011] The requirements of the chemical and pharmaceutical industry nowdemand weighings of 1 to 2 mg with precisions which can be of the orderof 0.1 to 0.2 mg, i.e. far beyond the performance capabilities of powderdispensers of the prior art.

[0012] The Applicant has discovered surprisingly and has developed anovel powder dosing device with which it is possible to satisfy the newrequirements imposed by the chemical and pharmaceutical industry forweighing of products.

[0013] Such a dosing device is particularly suitable for aliquoting froma collection of chemical compounds or for fractionation from storageflasks. It will be able to be used with powders or small solids of verydifferent grain sizes and different appearances, for example talc,lactose, cornstarch, or sand. In this patent application, the term“powder” designates powders or small solids, such as those mentioned byway of example above, with a grain size smaller than the thread and theradius of the endless screw.

[0014] The present patent application therefore relates to a dosing cap,comprising a body having a first end face designed to be brought intocommunication with a powder container, a second end face which, togetherwith the first end face, defines at least one feed hopper which widenstoward the first end face, the feed hopper supplying at least oneendless screw, and at least one opening. The cap according to theinvention is characterized in that the opening is positioned on thesecond end face, in communication with the endless screw.

[0015] The present patent application also relates to a dosing devicecomprising a cap according to the invention and a powder container.

[0016] Without being bound by any theory, the Applicant has found thatby placing the dispensing opening in the second end face of the body ofthe cap, rather than in the side of the body of the cap, in the axis ofand at the end of the endless screw, the flow is better governed and amuch finer degree of control is achieved. This makes it possible to dosemuch smaller quantities of powders, and to do so with a high level ofprecision.

[0017] More specifically, the device comprising the cap according to theinvention makes it possible to dose powder masses of significantly lessthan 5 mg, particularly of less than 3 mg, even of about 1 to 2 mg. Theweighing precision can be below 1 mg, preferably below 0.5 mg, morepreferably of the order of 0.1 to 0.2 mg, for most of the weighingoperations (the nonstandard weighing operations are those in which thedesired precision has not been achieved). Most of the weighingoperations is defined as being more than 50% of the weighing operationsperformed, preferably at least 75%, more preferably at least 85%, of theweighing operations. The maximum figure of 100% of the weighingoperations may even be achieved in some cases.

[0018] In addition to the possibility of weighing smaller masses, withimproved precision, the device according to the invention, provided withthe dosing cap according to the invention, also saves a great deal oftime and permits better preservation of the powders to be sampled bylimiting their manipulation.

[0019] The device according to the invention can be coupled to anautomatic system, which is run by software, in order to facilitate itscontrol and to fully automate the weighing operations.

[0020] During the dispensing, it is particularly advisable to tap on orto vibrate the device in order to loosen the powder if necessary or toeliminate the stacking effects arising in the dosing cap or thecontainer. This improves the supply to the endless screw via the feedhopper. The powder can also be dispensed by vibrating or tapping on thedevice whether or not the screw is rotating. The act of vibrating ortapping on the device in fact allows the powder to advance along thethread of the endless screw and as far as the opening. The deviceaccording to the invention will thus advantageously comprise a devicepromoting the dispensing of the powder, in particular by tapping, forexample by means of a movable and retractable finger which can strikethe dosing cap, or the container communicating with the latter, forexample 4 times per second, and/or by vibration, in particular by meansof a holding fork of the device.

[0021] The device according to the invention can also be provided withan agitator placed in the feed aperture. This agitator will haveprincipally two functions by which the dosing can be adjusted.

[0022] The first function of the agitator is that of eliminating thestacking effects in the feed aperture as these are detrimental toefficient dispensing of the powder.

[0023] The second function of the agitator is that of supplying or evenfilling the endless screw.

[0024] This agitator can advantageously be a rotary element rotatingabout an axis substantially perpendicular to the first and/or second endface. A substantially perpendicular axis is understood as being an axisintersecting the first and/or second end face at an angle of 90°±45°.

[0025] The agitator can be driven by means of a motor which may or maynot be connected to a computer controlling its rotation depending on thedosing requirements. In the preferred embodiments, the agitator isselected from the group consisting of an endless screw, a drill, or arod equipped with vanes.

[0026] When the powder dosing device is not in use, the cap can becompletely or partially covered by a hood which closes the opening offand thus prevents contamination by dust or ambient air.

[0027] The powder container can be of any size or shape and can beconstructed of any material which is thermally stable under theconditions of storage and use and is chemically inert to the powderswhich it contains. The container may in particular be any pill box orflask commonly used in collections of chemical compounds. By way ofexample, mention may be made of the glass pill boxes, for example withneck, of the BV18 Pharma type. The skilled person will be easily able toadapt the dimensions of the dosing cap to the container used or providean intermediate part for adapting a given cap to a given container.Thus, the dosing cap according to the invention will be able to beadapted to any pill box in the user's possession.

[0028] The cap according to the invention can be provided with a meansensuring leaktightness between the cap and the container during use.Such a means can be a lip, for example a washer.

[0029] The first end face of the body of the cap is open completely orpartially in order to permit communication between, on the one hand, thecontainer containing the powder to be dispensed, and, on the other hand,the feed hopper.

[0030] The first end face can be fixed to the container containing thepowder by any known means, for example by means of a screw thread, byclipping together, adhesive bonding, molding, preferably by means of ascrew thread.

[0031] The body of the cap can have an indicator on its outer surface inorder to permit positioning of the cap when it is used in an automaticsystem.

[0032] The endless screw preferably extends through the dosing cap on anaxis forming an angle substantially equal to 90°±45° relative to thevertical central axis intersecting the first and second end faces of thecap. This angle is more preferably equal to 90°.

[0033] The diameter and the pitch of the endless screw can be modifieddepending on the type of powder to be dispensed. The endless screwpreferably has a diameter close to its pitch. It can transport thepowder in one direction or the other, depending on the direction ofrotation applied to the screw. The direction of dispensing of the screwis defined as being that permitting the transport of the desired producttoward the dispensing opening.

[0034] The endless screw can also comprise a transmission memberdesigned to permit its rotation. This transmission member can forexample be a recess at one end of the endless screw and on its axis.This recess is preferably cross-shaped. If the product is dispensedexclusively by vibration or tapping, the transmission member may beabsent.

[0035] The device can be coupled, if appropriate by way of thetransmission member of the endless screw, to a device by which it ispossible to control and vary the angle of increment of rotation or thespeed of rotation of the endless screw by action of a rotary movement onthe transmission member or the force or frequency of vibration ortapping. Under these conditions, the movement of the endless screwand/or the vibration or tapping of the device are subject to theweighing indications of the balance via an external signal, and they arestopped when the desired powder mass is achieved.

[0036] The device according to the invention can also be coupled to oneor more antistatic devices, generating an electrical field promoting thedispensing of the powder. Without being bound by any particular theory,the Applicant believes that the powders to be dosed are naturallycharged or that the friction exerted by the grains of the product to bedispensed on the elements of the device generates charged entities. Thecharges induce forces leading in particular to agglomeration of thegrains or to magnetization of the grains in contact with the elements ofthe device. The device according to the invention is thus preferablyequipped with at least one antistatic device placed on the cap at theoutlet of the dispensing opening and generating an electrical fieldmaking it possible to channel the movement of the particles. In order tocover the whole of the dispensing opening, two antistatic devices willpreferably be used. An antistatic device can be a pointed ionizing probegenerating an electrical field of 4 kV, for example.

[0037] The dosing cap can be of any size or shape. It can in particularhave the shape of a cone, of circular or noncircular cross section,delimited by a wall, a first end face, and a second end face. These endfaces may or may not be perpendicular to the axis of the cone. Likewise,the cap can be made of any material thermally stable under theconditions of use and storage and chemically inert to the powders to bedosed. This material can in particular be a polymer material such aspolyethylene, polypropylene, fluoropolymers, for examplepolytetrafluoroethylene (teflon©). Each part can be molded. In apreferred embodiment, the body of the cap is made of a materialdifferent than that of the screw in order to limit the wear caused byfriction of two identical materials.

[0038] The opening positioned on the second end face of the dosing capcan be of any shape, in particular in the shape of a triangle,quadrilateral, circle, ellipse, or any other shape.

[0039] In a preferred embodiment of the cap and of the device accordingto the invention, the opening is in the shape of a triangle centered onthe axis of the endless screw and having an angle opening in thedirection of dispensing of the screw. The triangle shape permitsdispensing of a wide range of powders of widely varying grain sizes. Byway of an indicative and nonlimiting example, the powders generallydosed by means of this appliance are made up of particles with adiameter of less than or equal to 100 μm.

[0040] In another preferred embodiment, the opening is a trianglecentered on the axis of the endless screw and having an angle opening inthe direction of dispensing of the screw, and formed within a thicknessless than the full thickness of the second end face, toward the insideof the cap.

[0041] According to a particular embodiment of the invention, the dosingcap (1) comprises a means of closing off all or part of the opening(12), thus making it possible to modify the surface area of the openingbefore, during or after operation of the dosing cap.

[0042] This closure means can for example comprise at least one elementcovering all or part of the second end face (5). This closure means ismounted so as to be movable relative to the second end face, either in apivoting movement or in translation. The closure means comprises athrough-hole which can be positioned opposite the opening (12). Possibleexamples of such closure means are a diaphragm shutter of the cameratype or a slide shutter of the types known to the skilled person.

[0043] The powder dosing dispenser according to the invention works inthe following way:

[0044] the container containing the powder to be dispensed and equippedwith the dosing cap is placed vertically, the second end face and thedispensing opening being directed downward,

[0045] the endless screw is supplied with powder through the feed hopperand is set in rotation about its longitudinal axis, by any suitablesystem, in a direction of rotation permitting the dispensing of thepowder through the opening. Alternately, the dispensing is obtained byvibration or tapping of the device. The container receiving the powdercan be placed on the pan of a balance in order to continuously monitorthe dispensing,

[0046] once the desired mass of powder has been dispensed, the rotationof the endless screw and/or the vibration or tapping are stopped,

[0047] the device is ready for a new operation: it can be stored away,or it can be used to dispense a further, identical or different dose.

[0048] When a dosing operation has been concluded, the endless screw ispreferably set in rotation in the direction counter to that inducing thedispensing, so that the powder situated near the end of the endlessscrew is returned to the feed hopper. Simultaneously, the dosing deviceis turned upside down while the rotation of the endless screw ismaintained. The dosing cap is, if appropriate, held in place by the hoodprovided for this purpose. The result of this procedure is that thepowder remaining in the endless screw is reintroduced via the feedhopper into the container containing the powder and is isolated fromcontamination.

[0049] If the dosing dispenser comprises at least one antistatic device,said antistatic device can remain functioning permanently for theduration of use of the dosing dispenser (for example 100 successivedosing operations).

[0050] The invention will now be described in more detail with referenceto the figures.

[0051]FIG. 1 is a side view, in cross section, of an embodiment of thedosing device according to the invention.

[0052]FIG. 2 is a side view, in cross section, and at a different angle,of the embodiment of the dosing device according to FIG. 1.

[0053]FIG. 3 is an exploded side view of the embodiment of the dosingdevice shown in FIG. 1.

[0054]FIG. 4 is a view of the second end face of the cap of the dosingdevice in the particular embodiment of the dosing device in FIG. 1.

[0055]FIGS. 5a, 5 b, 5 c are side views, in cross section, of the powderdosing cap in operation.

[0056]FIG. 1 shows an embodiment of a dosing device when it is not inoperation. In this particular embodiment, the cap (1) is a cylinder. Thebody (3) has a first end face (4) and a second end face (5) delimiting,together with the first end face, a conical feed hopper (6) widenedtoward the first end face. The feed hopper (6) supplies the endlessscrew (7) whose axis is shown in the plane of the paper. The endlessscrew communicates with an opening (12). The first end face (4) isequipped with a thread (9) and is screwed onto a powder container (10).

[0057]FIG. 2 shows the dosing device from FIG. 1 at a different angle.The reference numbers have the same meanings. The endless screw (7) isshown in an axis perpendicular to the paper and is equipped with across-shaped transmission member (8) designed to permit its rotation. Awasher (11) ensures leaktightness when the cap is fixed on the container(10). The dosing cap is equipped with a hood (2) which is a cylinderdesigned to cover the body (3) and prevent contamination of the powderor of the equipment by dust or ambient air.

[0058]FIG. 3 is an exploded view showing the hood (2), the body (3) ofthe dosing cap from FIG. 1, the endless screw (7), the washer (11) forleaktightness, and the container (10).

[0059] In FIG. 4, the second end face (5) of the dosing cap comprisesthe triangle-shaped dispensing opening (12) centered on the axis of theendless screw and having an angle opening in the direction of dispensingof the endless screw (7). In this embodiment, a first rectangular recessis formed within part of the thickness of the second end face. Thetriangle-shaped opening is formed within the remaining thickness, towardthe inside of the cap. The indicator (13) is a notch formed on the outersurface of the body (3). The device for controlling and varying theangle of increment of rotation or the speed of rotation of the endlessscrew is a cross-shaped point (14) adapted to the cross-shapedtransmission member of the endless screw.

[0060]FIGS. 5a, 5 b, 5 c illustrate how a dosing cap operates. As hasbeen explained above, the second end face and the opening of the cap aredirected downward during operation. In FIG. 5a, the cross-shaped point(14) drives the endless screw (7) in a rotation movement about its axiswhich is supplied with powder through the feed aperture (6). In FIG. 5b,the powder is entrained by the endless screw, in the direction ofdispensing, toward the triangle-shaped opening (12). In FIG. 5c, thepowder is dispensed through the dispensing opening (12).

EXAMPLE

[0061] A dosing cap according to the invention, adapted to standardflasks having a neck of the BV18 Pharma type, comprising a molded bodymade of polypropylene and an endless screw made of polyethylene having adiameter and a screw thread both of about 5 mm is used to independentlydose 2 mg of lactose and 2 mg of cornstarch.

[0062] Although the means of measuring the results have not beencompletely optimized, the following nonlimiting results were obtained:

[0063] the lactose was dosed at 2 mg with a precision of ±0.07 mg for85% of the measurements, and with a precision of ±0.1 mg for 100% of themeasurements;

[0064] the cornstarch was dosed at 0.2 mg with a precision of ±0.15 mgfor more than 90% of the measurements.

[0065] Moreover, the time saved compared to when using devices of theprior art was evaluated at 30%.

1. A powder dosing cap (1), comprising a body (3) having a first end face (4) designed to be brought into communication with a powder container (10), a second end face (5) which, together with the first end face (4), defines at least one feed hopper (6) which widens toward the first end face (4), the feed hopper (6) supplying at least one endless screw (7), and at least one dispensing opening (12) for the powder to be dispensed, characterized in that the opening (12) is positioned on the second end face (5) in communication with the endless screw (7).
 2. The powder dosing cap (1) as claimed in claim 1, wherein the opening. (12) has the shape of a triangle, quadrilateral, circle or ellipse.
 3. The powder dosing cap (1) as claimed in either one of claims 1 and 2, wherein the opening (12) has the shape of a triangle centered on the axis of the endless screw (7) and having an angle opening in the direction of dispensing of the endless screw (7).
 4. The powder dosing cap (1) as claimed in any one of claims 1 through 3, wherein the opening (12) is formed within a thickness less than the full thickness of the second end surface (5), toward the inside of the cap (1).
 5. The powder dosing cap (1) as claimed in any one of claims 1 through 4, comprising a means of closing all or part of the opening (12) in order to permit modification of the surface area of said opening (12).
 6. The powder dosing cap (1) as claimed in claim 5, wherein the closure means comprises at least one element covering all or part of the second end face (5), said element being movable relative to the second end face (5) and having a through-hole which can be positioned opposite the opening (12).
 7. The powder dosing cap (1) as claimed in claim 6, wherein the closure means is chosen from between a diaphragm shutter of the camera type or a slide shutter.
 8. The powder dosing cap (1) as claimed in any one of claims 1 through 7, wherein the endless screw (7) can function by being rotated in one direction or in the opposite direction.
 9. The powder dosing cap (1) as claimed in any one of claims 1 through 8, wherein the endless screw (7) comprises a transmission member (8) designed to permit rotation of the endless screw (7).
 10. The powder dosing cap (1) as claimed in any one of claims 1 through 9, wherein the endless screw (7) is coupled to a device (14) by means of which it is possible to vary and control the angle of increment of rotation or the speed of rotation of the endless screw (7) by acting on the transmission member (8) giving a rotary movement of the screw and/or is coupled to a device promoting the dispensing of the powder.
 11. The powder dosing cap as claimed in any one of claims 1 through 10, further comprising a device promoting the dispensing of the powder, in particular by vibration and/or by tapping of the dosing cap (1) and/or of the powder container (10).
 12. The powder dosing cap as claimed in claim 11, wherein the device promoting the dispensing of the powder by tapping is a retractable finger.
 13. The powder dosing cap as claimed in claim 11, wherein the device promoting the dispensing of the powder by vibration is a holding fork.
 14. The powder dosing cap as claimed in any one of claims 1 through 13, further comprising an agitator placed inside the feed hopper.
 15. The powder dosing cap as claimed in claim 14, wherein the agitator is an element rotating about an axis substantially perpendicular to the first and/or second end face.
 16. The powder dosing cap as claimed in claim 15, wherein the agitator is selected from the group consisting of an endless screw, a drill, or a rod equipped with vanes.
 17. The powder dosing cap (1) as claimed in any one of claims 1 through 16, further comprising at least one antistatic device, such as an ionizing probe or point.
 18. The powder dosing cap (1) as claimed in any one of claims 1 through 17, wherein the parts of which it is made up are of a material which is thermally stable under the conditions of use and of storage and chemically inert to the powders to be dosed, in particular of a polymer material such as polyethylene, polypropylene, and fluoropolymers, such as polytetrafluoroethylene (teflon©).
 19. A powder dosing device (1) comprising a powder container (10) brought into communication with a dosing cap (1) as claimed in any one of claims 1 through
 18. 20. Use of the powder dosing device as claimed in claim 19, for dosing powders having masses of less than 5 mg, preferably of less than 3 mg, and more preferably of between 1 and 2 mg approximately, with a weighing precision below 1 mg, preferably below 0.5 mg, and more preferably of the order of 0.1 to 0.2 mg, for over 50%, preferably at least 75%, more preferably at least 85%, of the weighing operations carried out.
 21. Use of the dosing cap (1) as claimed in any one of claims 1 through 18 and 20 or of the device as claimed in claim
 19. 